Cephaloscyllium ventriosum are not commercially fished, but are often caught as bycatch in the lobster and crab fishing industries. Although this species is not currently threatened or endangered, bycatch poses a potential conservation risk due to slow reproduction and the small number of young produced each year.
US Federal List: no special status
CITES: no special status
IUCN Red List of Threatened Species: least concern
Cephaloscyllium ventriosum can take in water or air as a means of escaping from predators, giving it the common name "swell shark." It hides in rocky caves and crevices and swallows water to expand its stomach if attacked. This behavior ensures that it is tightly jammed into crevices and cannot be pulled out. If these sharks are threatened when out in the open, they grab their tail in their mouths, to form a U-shape and swell with water, making themselves difficult to grab or manipulate. Sphincter muscles at both ends of the stomach trap the water. Relaxation of these muscles releases the water, returning the stomach to normal size (Bright 2000). If taken out of water, this species can also gulp air, which makes it swell up like a balloon. When this air is released, a barking sound results (Bright 2000). Swell sharks are also cryptically colored.
Swell sharks are preyed on by marine mammals, including sea lions, seals, and larger sharks. Developing swell shark embryos are sometimes eaten by marine snails, which bore through the egg casing.
Known Predators:
Anti-predator Adaptations: cryptic
Cephaloscyllium ventriosum is a large, strongly variegated catshark. Swell sharks are yellow-brown with many dark spots and occasional light spots on the body, fins, and underside of head and abdomen. Juveniles are usually lighter in color than mature adults ("MarineBio.org" 2005). The snout is very short and broadly rounded with nasal flaps reaching the mouth. This species has two dorsal fins, the second much smaller (Compagno 1984). The maximum size is at least 100 cm, with adult males ranging from 82 to 85 cm. The size at hatching is 14 to 15 cm (Compagno 1984).
Range length: 100 (high) cm.
Average length: 82 to 85 cm.
Average basal metabolic rate: 44.3 cm3.O2/g/hr.
Other Physical Features: ectothermic ; heterothermic ; bilateral symmetry
Sexual Dimorphism: sexes shaped differently
There is no information available on the lifespan of C. ventriosum.
Cephaloscyllium ventriosum is a benthic and epibenthic shark living in warm-temperate and subtropical continental waters. The depth range of this species varies from inshore to 457 m and is most common at depths of 5 to 37 m. Cephaloscyllium ventriosum is sometimes found in algal-covered bottom without kelp, but prefers rocky, algal-covered areas of kelp beds. This species is usually found motionless in rocky caves and crevices during the day, and swims slowly through bottom algae or in open water close to the bottom at night (Compagno 1984).
Range depth: 457 (high) m.
Average depth: 5-37 m.
Habitat Regions: temperate ; tropical ; saltwater or marine
Aquatic Biomes: benthic ; coastal
Other Habitat Features: caves
Cephaloscyllium ventriosum (swell shark) is found in the eastern Pacific Ocean, ranging from Central California, in the Monterey Bay, to southern Mexico and central Chile (Compagno 1984).
Biogeographic Regions: pacific ocean (Native )
Cephaloscyllium ventriosum feeds on bony fishes, alive and dead, and crustaceans. Young feed on mollusks, crustaceans, and small fish. Swell sharks have large mouths and relatively small, sharp-pointed teeth that could handle large prey, but these sharks seem incapable of dashing after active prey (Compagno 1984).
It is thought that this species specializes in catching diurnal bony fishes that are relatively inactive and unresponsive at night. The nocturnal activity pattern of this slow and weak-swimming species aids in capture of prey (Compagno 1984). Swell sharks often are seen remaining motionless on sea floor, waiting for prey to wander by or be swept into their mouths by currents. They have also been known to enter lobster traps to eat lobsters (Bester, 2006).
Animal Foods: fish; carrion ; mollusks; aquatic crustaceans
Primary Diet: carnivore (Piscivore , Eats non-insect arthropods)
There is little information available about the ecosystem role of C. ventriosum. They are both predators on fish, crustaceans, and mollusks, and are preyed on by larger predators.
Cephaolscyllium ventriosum is not fished commercially, and although this species is ocassionally caught by sportfishers and divers, the flesh is probably not utilized (Compagno 1984).
There are no known adverse effects of C. ventriosum on humans, as they only become aggressive when harassed.
Cephaloscyllium ventriosum is oviparous and lays eggs in large, greenish-amber egg-cases which hatch in 7.5 to 10 months depending on the water temperature. The young have a double row of enlarged toothlike projections down the back that aid the young in forcing their way out of the egg-cases (Compagno 1984).
There is little information available on how C. ventriosum communicates and perceives the environment. Sharks, in general, have keen chemical perception abilities and can sense electronic signals as well.
Perception Channels: visual ; tactile ; chemical ; electric
There is little information available for the mating system of C. ventriosum.
There is little information about the reproductive cycle of C. ventriosum.
Range gestation period: 7.5 to 12 months.
Key Reproductive Features: iteroparous ; gonochoric/gonochoristic/dioecious (sexes separate); sexual ; fertilization (Internal ); oviparous
Although there is not much detailed information on parental investment in this species, female individuals of C. ventriosum anchor the egg cases (usually two) in a rocky, algae-covered location for protection until the eggs hatch. Egg cases have twisted tendril-like extensions on each of their four corners, which catch on seaweed and rocks, helping to keep the egg case from drifting. The newborn pups feed on mollusks and crustaceans immediately, with no assistance from either parent.
Parental Investment: no parental involvement; pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female)
The swell shark (Cephaloscyllium ventriosum) is a catshark in the family Scyliorhinidae. It is found in the tropical and subtropical eastern Pacific Ocean from between central California to southern Mexico, with an additional population off the coast of Chile.[1] As a defense, the swell shark is able to expand to approximately double its regular size by swallowing water.
When discovered in 1880, the swell shark was first described as Scyllium ventriosum, but was later changed to Cephaloscyllium ventriosum. The genus name comes from the Greek word kephale, which means "head", and skylla, which means a certain kind of shark. The species name comes from the Latin word ventrĭōsus, which means "large-bellied". The species name refers to its ability to enlarge itself by taking in water.[2]
The swell shark is found in the eastern Pacific Ocean, from the central California coast to southern Mexico.[1][2] There is an additional population off the coast of Chile.[2][3] It can be found between the depths of 5 m and 457 m, but is most common between 5 m and 37 m.[2][1]
Swell sharks are often found over algae-covered rocky bottoms where it hides in crevices during the day.[2]
Swell sharks are typically around 90 cm in length, with a maximum length of 110 cm.[2][3] They have flat, broad heads with large gold eyes that have nictitating eyelids.[2] Swell sharks have a yellow-brown coloration, with brown and white spots.[2] The spots cover their underside, but are not present on their fins.[2] Usually the younger sharks are lighter in color than the adults.[2] The gills of a swell shark are usually very small and tight.[2]
Every swell shark has around 55–60 teeth.[2] Teeth typically have three smooth cusps, but can have as many as five cusps.[2] The middle cusp is the longest.[2]
Head
Jaws
Lower teeth
Upper teeth
Swell sharks are nocturnal and sleep in rock crevices during the day, where their appearance allows them to be camouflaged.[2] They are very sociable and are commonly seen sleeping next to or on top of other sharks.[4][3]
The swell shark is oviparous, laying two green or amber flattened eggs at a time.[1][3] Fertilization occurs internally.[5] The egg cases become attached to kelp or the reef with tendrils. It has been suggested that the length of the tendrils depends on the amount of surf action the region is under.[4] After producing the egg case, no parental care is provided.[5] The egg case which contains the embryo is approximately 2.5 centimeters (0.98 in)–5.1 centimeters (2.0 in) by 7.6 centimeters (3.0 in)–13 centimeters (5.1 in).[2] The embryos will feed solely on yolk before they hatch.[3] The gestation time depends on water temperature but is typically between 9–12 months.[5] Pups have a double row of enlarged dermal denticles to help them exit the eggcase.[4][5] After hatching, the pup is approximately 15 cm in length and is fully self-sufficient.[4][5]
Swell sharks hunt at night for bony fish, molluscs, and crustaceans.[2][3] They will eat prey that is dead or alive.[3] They feed either by sucking prey into their mouth or by waiting motionless on the sea floor with their mouth open, waiting to encounter prey.[2][4] Swell sharks have also been known to look for food in lobster traps.[2]
When the shark feels threatened, it will bend its body into a U–shape, grab its tail fin with its mouth, and suck in water.[2] Doing so causes the shark to enlarge in diameter and makes it much harder for predators to bite or dislodge.[2][4] The swell shark is capable of swelling by using water or air, which is stored in the stomach until released.[2][4] When letting air out, the swell shark makes a dog-like bark.[2][5] Swell sharks are non-aggressive and are considered harmless to humans.[3][2][5]
Swell shark biofluorescence was first reported in 2014. Researchers presented species-specific emission patterns, indicating that biofluorescence potentially functions in intraspecific communication and assists camouflage.[7] The key fluorecent pigments in the swell shark and the chain catshark are a set of brominated kynurenine compounds that appear to be synthesized by the kynurenine pathway starting from 6-bromo-tryptophan.[6] The biochemical origin of 6-bromo-tryptophan in these species is not known.
There are no fishery operations that target swell sharks, however, they are occasionally caught as bycatch in lobster and crab traps, gillnets, and trawls.[2] Swell sharks are not typically consumed by humans due to the poor quality of meat.[1][2][5] Swell sharks are common in public aquariums, in part due to their longevity in captivity.[2][4] The IUCN has assessed the swell shark as "least concern".[1]
The swell shark (Cephaloscyllium ventriosum) is a catshark in the family Scyliorhinidae. It is found in the tropical and subtropical eastern Pacific Ocean from between central California to southern Mexico, with an additional population off the coast of Chile. As a defense, the swell shark is able to expand to approximately double its regular size by swallowing water.
